more like wolves of the sea, since they hunt in packs and often attack prey larger than them.

Wolves hunt to eat. Housecats hunt to eat but also for sport and fun and will very often not even consume their prey, as they are well fed by their owners. That's where the "cats of the sea" comment came from. Wolves are very risk-averse, and only hunt when they need to eat.

>Some go so far as to risk beaching themselves in order to snag a baby seal—not to consume, but simply to torture it to death.

This is very much housecat behavior.

Given how intelligent we believe them to be, it seems likely to me that mental stimulation (including perhaps "recreation") when not acquiring food is quite meaningful to them.